This invention relates to the reduction of alkaline normality of a lithium bromide solution as commonly employed in an absorption refrigeration system.
Generally, in most absorption systems utilizing lithium bromide as a working fluid, the solution is inhibited to reduce the harmful effects of the solution upon the wetted metal surfaces of the machine. In this type of system, the water in the solution reacts with metals, particularly iron, to form corrosives. In an acid or neutral solution, the corrosive reaction occurs at a relatively rapid rate. In fact, iron corrosion can take place at such a rate that the operating life of the machine could be drastically reduced. Furthermore, non-condensible hydrogen is released within the solution in considerable amounts which can act to interfere with, and thus seriously reduce, the efficiency of the absorptive process.
It is the common practice in the art to add lithium hydroxide to the solution to retard the corrosive effects and thus extend the life of the system. Generally, sufficient lithium hydroxide is added to bring the solution pH to a level of between 11 and 13. However, even with the addition of lithium hydroxide, the rate at which hydrogen is produced within the solution is excessive. To eliminate the hydrogen effect, either lithium chromate or lithium nitrate is added to the solution in sufficient quantities to completely eliminate the hydrogen generated. Thus, in most lithium bromide solutions, lithium hydroxide is added as the primary inhibitor to retard corrosion and either lithium chromate or lithium nitrate added as a secondary inhibitor to control low level corrosion and eliminate hydrogen generation.
It has been found that solutions containing inhibitors exhibit an increase in the hydroxide normality with usage. It is therefore important to periodically reduce or lower the alkalinity of the solution in order to preserve high operating efficiency. One of the most common techniques utilized in lowering alkalinity is the periodic addition of hydrobromic acid to the solution. Because of the volatile nature of the additive, this procedure must be practiced with caution. It also requires exacting procedures to insure that the proper dilution is obtained within the solution. In certain cases, improper addition of hydrobromic acid can affect the solution cation constituents and produce an erratic behavior within the system or results in the production of non-condensible gases which serve to interfere with the absorption process. Similarly, any air leakage into the system during the adjustment period will have a detrimental effect upon the solution. Finally, the commercial availability of hydrobromic acid is extremely limited and expensive.